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TMeshSimplification

Implementation of Garland & Heckbert Quadric Error Metric (QEM) Triangle Mesh Simplification

API > API/Plugins > API/Plugins/DynamicMesh

Inheritance Hierarchy

References

   
Module DynamicMesh
Header /Engine/Plugins/Runtime/GeometryProcessing/Source/DynamicMesh/Public/MeshSimplification.h
Include #include "MeshSimplification.h"

Syntax

template<typename QuadricErrorType>  
class TMeshSimplification : public UE::Geometry::FMeshRefinerBase

Remarks

Implementation of Garland & Heckbert Quadric Error Metric (QEM) Triangle Mesh Simplification

Variables

  Type Name Description
Public variable bool bAllowSeamCollapse If true, we allow UV and Normal seams to collapse during simplification.
Protected variable bool bHaveBoundary  
Public variable bool bPreserveBoundaryShape If true, we try to keep boundary vertices on boundary.
Public variable bool bPreventTinyTriangles Controls whether we disallow creation of triangles with small areas inside edge operations.
Public variable bool bRetainQuadricMemory If false, face and vertex quadrics are recomputed in the neighborhood of each collapse, definitely slower but maybe higher quality
Public variable ESimplificationCollapseModes CollapseMode Controls the method used when selecting the position the results from an edge collapse.
Protected variable int COUNT_COLLAPSES Testing/debug/profiling stuff profiling functions, turn on ENABLE_PROFILING to see output in console
Protected variable int COUNT_ITERATIONS  
Protected variable TArray< QEdge > EdgeQuadrics  
Protected variable FIndexPriorityQueue EdgeQueue  
Public variable EGeometricErrorCriteria GeometricErrorConstraint Geometric error measurement/check to perform before allowing an edge collapse
Public variable double GeometricErrorTolerance Tolerance to use in geometric error checking
Public variable EEdgeRefineFlags GroupBoundaryConstraint  
Protected variable TArray< bool > IsBoundaryVtxCache  
Public variable EEdgeRefineFlags MaterialBoundaryConstraint  
Protected variable int MaxEdgeID  
Protected variable float MaxErrorAllowed  
Public variable EEdgeRefineFlags MeshBoundaryConstraint When using the constraint system, these options will apply to the appropriate boundaries.
Protected variable double MinEdgeLength  
Protected variable const int ModuloPrime We are using a modulo-index loop to break symmetry/pathological conditions.
Protected variable FDynamicMeshNormalOverlay * NormalOverlay  
Protected variable double SeamEdgeWeight  
Protected variable TMap< int, FSeamQuadricType > seamQuadrics  
Protected variable ETargetModes SimplifyMode  
Protected variable int TargetCount  
Protected variable TArray< double > triAreas  
Protected variable TArray< FQuadricErrorType > triQuadrics  
Protected variable TArray< FQuadricErrorType > vertQuadrics  

Constructors

  Type Name Description
Protected function    
Public function    

Functions

  Type Name Description
Protected function Virtual void

ApplyToProjectVertices ( const TFunction< void(int)>& apply_f
)

  
Protected function Const FQuadricErrorType Uses pre-computed vertex, face and seam quadrics to construct the edge quadric.
Protected function Const bool

CanCollapseEdge ( int edgeID,
int a,
int b,
int c,
int d,
int t0,
int t1,
int& collapse_to
)

 Figure out if we can collapse edge eid=[a,b] under current constraint set This depends on the base class function FMeshRefinerBase::CanCollapseEdge, but includes additional restrictions specified by the CollapseMode of this simplifier.
Protected function bool

CheckIfCollapseWithinGeometricTolerance ( int vid,
int vother,
const FVector3d& newv,
int tc,
int td
)

 Check if edge collapse would violate geometric error criteria
Protected function ESimplificationResult

CollapseEdge ( int edgeID,
FVector3d vNewPos,
FDynamicMesh3::FEdgeCollapseInfo& collapseInfo,
int32 RequireKeepVert
)

 Collapse given edge.
Protected function Const FQuadricErrorType

ComputeFaceQuadric ( const int tid,
FVector3d& nface,
FVector3d& c,
double& Area
)

  
Protected function Virtual void Top-level function that does the simplification
Protected function Const bool This just lets us write more concise code
Public function Virtual void

FastCollapsePass ( double MinEdgeLength,
int Rounds,
bool bMeshIsClosedHint,
uint32 MinTriangleCount
)

 Does N rounds of collapsing edges longer than fMinEdgeLength.
Protected function Virtual void Project vertices onto projection target.
Protected function Virtual int

GetNextEdge ( int CurEdgeID,
bool& bDoneOut
)

  
Protected function Virtual FVector3d

GetProjectedCollapsePosition ( int vid,
const FVector3d& vNewPos
)

 Used by collapse-edge to get projected position for new vertex
Protected function FVector3d

GetProjectedPoint ( const FVector3d& pos
)

  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Const bool

IsBoundaryVertex ( int vid
)

  
Protected function void

OnEdgeCollapse ( int edgeID,
int va,
int vb,
const FDynamicMesh3::FEdgeCollapseInfo& collapseInfo
)

  
Protected function Virtual void

OnEdgeCollapse ( int edgeID,
int va,
int vb,
const FDynamicMesh3::FEdgeCollapseInfo& collapseInfo
)

 Subclasses can override these to implement custom behavior...
Protected function Virtual void  
Protected function FVector3d

OptimalPoint ( int eid,
const FQuadricErrorType& q,
int ea,
int eb
)

 Return point that minimizes quadric error for edge [ea,eb]
Protected function void

Precompute ( bool bMeshIsClosed
)

  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void

ProjectVertex ( int vID,
IProjectionTarget* targetIn
)

  
Protected function bool Remove an isolated triangle.
Protected function Virtual void  
Public function Virtual void

SimplifyToEdgeLength ( double MinEdgeLength
)

 Simplify mesh until no edges smaller than min length remain. This is not a great criteria.
Public function Virtual void

SimplifyToMaxError ( double MaxError
)

 Simplify mesh until the quadric error of an edge collapse exceeds the specified criteria.
Public function Virtual void

SimplifyToMinimalPlanar ( double CoplanarAngleTolDeg,
TFunctionRef< bool(int32 EdgeID)> EdgeFilterPredicate
)

 Maximally collapse mesh in a way that does not change shape at all.
Public function Virtual void

SimplifyToTriangleCount ( int TriangleCount
)

 Simplify mesh until we reach a specific triangle count.
Public function Virtual void

SimplifyToVertexCount ( int VertexCount
)

 Simplify mesh until it has a specific vertex count
Protected function Virtual int  
Protected function Virtual void Update queue weight for each edge in vertex one-ring and rebuild and quadrics necessary

Classes

  Type Name Description
Protected struct FEdgeError    
Protected struct QEdge Internal class for priority queue  

Enums

  Type Name Description
Public enum EGeometricErrorCriteria Ways to measure geometric error  
Public enum ESimplificationCollapseModes    
Protected enum ETargetModes    

Typedefs

Name Description
FQuadricErrorType  
FSeamQuadricType  
RealType  

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